Swinging t-square

ABSTRACT

A geometrical instrument useful as a building tool has a Tsquare with a protractor head revolubly mounted on a stub shaft projecting from an adjacent rectangular panel, the blade of the T-square depending from the mounting. Stop means are combined with the shaft for selectively locking the T-square to the panel.

United States Patent 1191 1111 3,828,436

King Aug. 13, 1974 SWINGING T-SQUARE 1,123,269 1/1915 Frame 33/400 1 1 Inventor: Calvin King, 300 Edgewood 83; 313521128 55132? $12.11,, 5633 Hope, 71801 3,103,749 9/1963 Dillemuth 33/347 22 Filed: Aug.30, 1973 [21] Appl. No.: 393,112 Primary Examiner-Harry N. Haroian Related US. Application Data Continuation-impart of Ser. No. 297,728, Dec. 24, i972, abandoned.

References Cited UNITED STATES PATENTS 5/1911 Johnson 33/370 Attorney, Agent, or Firm-Ralph R. Pittman ABSTRACT 12 Claims, 4 Drawing Figures PAIENIEnms: awn

sum 2 or z SWINGING T-SQUARE BACKGROUND This application is a continuation-in-part of applicants now abandoned application Ser. No. 297,728, filed Dec. 24, 1972. g

The swinging T-square described herein relates to a pendulate angle-measuring tool particularly adapted for use by carpenters, millwrights and others engaged in work requiring plumbline determinations and associated angle measurements, such work including the layout of rafters for roofs, stairbuilding and similar construction activities.

A large variety of combined protractors and T- squares have been described in the prior art, most of which are intended for drafting table application and not adaptable for use as construction tools. The much smaller number of prior art devices specifically structured for use as builders measuring tools appear to require the use of both hands of the operator for measurements along a single vertical plane. In addition, for holding the relatively movable members to a definite angular relationship, the prior art devices employ some type of screw-threaded fittings, such as wingnuts or thumbscrews, the use of which necessitates great care to avoid destroying the integrity of a measurement and therefore results in an unavoidable time-consuming procedure.

SUMMARY OF THE INVENTION The tool described herein utilizes a spring holding a stopper in a normal position permitting a free-swinging.

relationship between the measurement members, the stopper being rectilinearly movable into a complementary recess to lock the members in place for holding them at some selected angular relationship. The T- square of the tool is journalled on a low friction ball bearing, equal parts of the head of the T-square projecting on either side of the ball bearing to balance the T-square thereon, and the blade of the T-square extends downwardly from the bearing in a similar balanced disposition.

The T-square is swingably mounted on the lower panel of a two-panel base, the upper panel of the mounting base being hinged to the lower panel along a normally horizontal axis. Both panels are rectangular in shape, the respective longer edges of each rectangle being disposed in parallel with one another, and the respective shorter edges defining coextensive parallel planes. The upper panel is swingable from a coplanar position with the lower panel through an angle of more than ninety degrees from the face of the lower panel, thus enabling the engagement of the tool along the top plate of a building member.

The head of the T-square defines a protractor semicircle integral with the blade, and this member, as well as the panels, may be formed of a high impact plastic material, such as Lexan or Plexiglas.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a front elevational view of the invention, illustrating the protractor head and the depending blade of the T-square, shown with the blade in the plumb or vertical position, the protractor reading being zero angle, a reading which appears when either the lower edge of the lower panel or the upper edge of the upper panel engages a horizontal planar surface;

FIG. 2 is a side elevation view of the invention, shown partly in section, illustrating the hinged panels of the mounting and the relationship of the elements employed for selectively locking the T-square to its mounting, the stopper being shown in the normal disengaged position;

FIG. 3 is a section taken along the line 33 of FIG. 2, showing additional structural features of the stopper and its mounting on the shaft; and

FIG. 4 is a fragmentary section illustrating the stopper in the locking position for holding the T-square in a selected position relative to the panel mounting.

DESCRIPTION OF THE PREFERRED EMBODIMENT In brief, the invention is a mechanical structure embodying a protractor type T-square freely swingable from a shapeable two-panel mounting, the T-square being releasably lockable in a position in which the T- square bears a specific angular relationship to the mounting from which it is pendulated, the angular relationship being readable from a protractor-head on the T-square.

Referring in more detail to the drawing, the invention is a geometrical measuring tool comprising structural members including: the T-square, generally indicated by the numeral 11; the panel members on which the T- square is mounted, generally indicated by the numeral 10; and a stopper for releasably holding the T-square in a selected position relative to the-mounting members, generally indicated by the numeral 31 (FIG. 2).

The head 12 of the T-square has a semicircular upper margin bearing the angular indicia l6 and 17, the marks being spaced respectively at one degree intervals and 7 /2 degree intervals, and depending from the head 12 is the blade 13 of the T-square, bearing the linear indicia 44 along the respective longitudinal margins thereof. The bubble level 15, nested in the recess 14, extends transversely across the lower end portion of the blade 13.

The T-square mounting 10 is disposed spatially adjacent to the rear surface of the T-square, and includes a lower plane-parallel panel 19 fixed in parallelism therewith, and an upper plane-parallel panel 18 of identical width and thickness hinged to the lower panel and swingable outwardly and downwardly away from upper end of the T-square.

The downwardly directed integral hinge knuckle 20 of the upper panel 18 is joined to the upwardly directed integral hinge knuckle 21 of by the hinge pin 22, this construction being provided along the respective adjacent end portions of the panels.

A limit stop 27 projects upward from the lower panel with its rear face coextensive therewith, the limit stop being disposed to permit swinging of the rear face of the upper panel only to and not beyond coplanar relation with the rear face of the lower panel, without, however, restricting rearward and downward swinging of the upper panel.

A bracket 23 is attached to the upper midmost portion of the upper panel 18, and has a forwardly projecting portion the upper surface of which is coplanar with the upper edge surface of the upper panel and a downwardly directed portion terminating below the upper edge of the upper panel. A nail 24 passes through the outer lower portion of the bracket and into an aperture The stub shaft 34 (FIG. 2) is rigidly secured to the lower panel 19, projecting normally forward therefrom and having a relatively short enlarged portion 35 for fixing the space between the panel and the T-square. A cylindrical boss 28 projects forwardly from a midportion of the T-square, and the shaft 34 passes concentrically through a central opening in the boss to a point beyond the forward end of the boss. A recess 41 opens into the boss from the rear, into which the ball bearing 36 is fitted, to thereby journal the T-square for revoluble movement about the fixed shaft 34.

The central opening extending through the boss 28 includes a microgrooved inwardly tapering recess 29, and a stopper 31 has a complementary microgrooved outwardly tapering portion 30 sized to cooperate with the recess 29 for locking the stopper 31 therein when the stopper is urged to engagement with the recess.

A helical reset spring 38 is fitted loosely around the shaft 34 between the inner surface of the stopper portion 30 and the concentric ring 37, the .latter being fixed to the shaft by the pin 40 (FIG. 2) adjacent to the outer surface of the bearing 36. The spring 38 lightly urges the stopper away from engagement with the boss 28, and the cotter key 39, extending through the shaft 34, limits the forward movement of the stopper 31.

A flat fingerhold portion 32 of the stopper 31 extends inwardly from its forward end to merge with the tapered portion 30, a window opening 33 being provided therebetween to permit in and out movement of the stopper along the shaft. As shown in FIGS. 3 and 4., a guide slot 42 extending along the forward end portion of the shaft receives a guide 43 of the stopper, thus precluding rotary movement of the stopper with respect to the shaft and limiting stopper movement to a rectilinear direction in and out of its cooperating recess.

The bracket 23 provides a centrally positioned projection for balancing the tool on a finger of the user, and when so held, the T-square moves as may be required about the shaft on the ball bearing to come to rest with the zero lines of the angular indicia coextensive with the index lines 45 on the lower panel, and the plumb position of the blade of the T-square is indicated by the bubble level 15. These conditions establish that the T-square is precisely balanced on its mounting, for the reason that the ball bearing is so low in friction that a T-square blade of very small mass is adequate to preclude spurious readings.

Assuming that the slope of the underside of a structural member is desired, the top edge of the upper panel is held against the surface, causing the T-square to turn about the shaft, the degrees of turning being.

readable from the angular indicia. If it is desired to retain the members in the indicated angular relationship, the stopper 31 is moved linearly inward to lock the T- square to the mounting. ln so doing, the concurrent deformation of the reset spring 38 does not prevent locking, as this spring is so coordinated with the microgrooved elements that it is effective only to prevent unwanted engagement of the elements as the tool is handled.

In similar fashion, the angular direction of the upper surface of a structural member may be determined, as may be the more convenient, by either one of two applications of the tool; thatis, by resting the lower edge of the lower panel on the member and reading the angle or, alternately, by swinging the upper panel downward to facial engagement with the member and similarly reading the angle. The bubble level 15 makes available a confirmation reading that the T-square blade is in the vertical position, and that the lower edge of the head of the T-square is in a horizontal position.

The hinged upper panel with the associated tacking attachment is particularly useful when the building requirements dictate a specific direction for a structural member being handled for fitting into a building, as the tool may be tacked to the structural member, leaving the workmans hands free to move and fix the member to the desired orientation as shown by the tool. An angle having been established as correct, the tool may be locked for application to other members, as desired. The locking of the tool is effected by a small rectilinear movement of the stopper, which action avoids subjecting the tool to any turning force with the attendant likelihood of inaccurate angular measurements.

What is claimed is:

1. A swinging T-square tool comprising an upstanding T-square having a planar rear wall surface, a semicircular head, a blade depending from the midsection of said head and a cylindrical boss projecting forwardly about the transverse center of volume of said T-square at the juncture of said head with said blade, panel means disposed in spatially adjacent parallelism with the rear wall surface of the T-square, a stub shaft rigidly secured to said panel means and projecting therefrom concentrically through said cylindrical boss, bearing means normally pendulously supporting said T-square on said shaft, and stop means rectilinearly movable along the shaft and engagable with the interior of said boss for releasably locking said T-square to said panel means.

2. The tool in accordance with claim 1, wherein the semicircular arc of the T-square head is subdivided as a protractor.

3. The T-square tool defined in claim 1, wherein an internal recess tapers inwardly from the forward end of said boss and said stop means has an externally tapered portion conforming to the internal surface of said recess, said stop means being reciprocably movable to either fit snugly into said recess or move therefrom.

4. The subject matter of claim 3, in which a guide slot extends longitudinally along the stub shaft and said stopper includes an inwardly projecting portion fitting into the guide slot.

5. The subject matter of claim 3, wherein a plurality of longitudinally extending microgrooves constitute the external surface of the tapered portion of said stopper.

6. The subject matter of claim 3, wherein a plurality of microgrooves extend longitudinally over the internal surface of said recess.

7. The swinging T-square tool in accordance with claim 3, including resilient means opposing movement of said stopper in the direction to enter said recess.

8. The tool in accordance with claim 1, in which said bearing means is a ball bearing structure interposed between said shaft and said boss.

9. A swinging T-square tool for use in an upright position, comprising inflexible upper and lower rectangular panels of equal width, a stub shaft rigidly secured to and projecting normally forward through the vertical centerline of the lower panel, bearing means revolubly supporting a T-square on said shaft and stop means rectilinearly movable along said shaft, said stop means coacting with said shaft to lock said T-square to said shaft, and T-square having a semicircular head through which said shaft extends, a blade depending from the midsection of said head and a planar rear wall surface disposed in spatially adjacent parallelism with the forward wall surface of the lower panel, said upper panel being hinged to the upper margin of the lower panel and swingable downwardly and outwardly between a position coplanar with the forward face of the lower panel and a position perpendicular thereto, and limit stops mounted on said lower panel in the path of movement of said upper panel, said stops limiting the upward and the lower edge of said lower rectangular panel. 

1. A swinging T-square tool comprising an upstanding T-square having a planar rear wall surface, a semicircular head, a blade Depending from the midsection of said head and a cylindrical boss projecting forwardly about the transverse center of volume of said T-square at the juncture of said head with said blade, panel means disposed in spatially adjacent parallelism with the rear wall surface of the T-square, a stub shaft rigidly secured to said panel means and projecting therefrom concentrically through said cylindrical boss, bearing means normally pendulously supporting said T-square on said shaft, and stop means rectilinearly movable along the shaft and engagable with the interior of said boss for releasably locking said T-square to said panel means.
 2. The tool in accordance with claim 1, wherein the semicircular arc of the T-square head is subdivided as a protractor.
 3. The T-square tool defined in claim 1, wherein an internal recess tapers inwardly from the forward end of said boss and said stop means has an externally tapered portion conforming to the internal surface of said recess, said stop means being reciprocably movable to either fit snugly into said recess or move therefrom.
 4. The subject matter of claim 3, in which a guide slot extends longitudinally along the stub shaft and said stopper includes an inwardly projecting portion fitting into the guide slot.
 5. The subject matter of claim 3, wherein a plurality of longitudinally extending microgrooves constitute the external surface of the tapered portion of said stopper.
 6. The subject matter of claim 3, wherein a plurality of microgrooves extend longitudinally over the internal surface of said recess.
 7. The swinging T-square tool in accordance with claim 3, including resilient means opposing movement of said stopper in the direction to enter said recess.
 8. The tool in accordance with claim 1, in which said bearing means is a ball bearing structure interposed between said shaft and said boss.
 9. A swinging T-square tool for use in an upright position, comprising inflexible upper and lower rectangular panels of equal width, a stub shaft rigidly secured to and projecting normally forward through the vertical centerline of the lower panel, bearing means revolubly supporting a T-square on said shaft and stop means rectilinearly movable along said shaft, said stop means coacting with said shaft to lock said T-square to said shaft, and T-square having a semicircular head through which said shaft extends, a blade depending from the midsection of said head and a planar rear wall surface disposed in spatially adjacent parallelism with the forward wall surface of the lower panel, said upper panel being hinged to the upper margin of the lower panel and swingable downwardly and outwardly between a position coplanar with the forward face of the lower panel and a position perpendicular thereto, and limit stops mounted on said lower panel in the path of movement of said upper panel, said stops limiting the upward and inward swingable movement of said upper panel to said coplanar position.
 10. The subject matter of claim 9, wherein fastening means for tacking the tool to an associated structural member is secured to the upper margin of the upper panel.
 11. The subject matter of claim 9, in which a bracket secured midway on the upper margin of the upper panel projects forwardly therefrom.
 12. The tool as set forth in claim 9, wherein the semicircular head of the T-square bears indicia means for indicating the angle of departure from the horizontal of the lower edge of said lower rectangular panel. 